title: Divergences in morphological changes and antioxidant responses in salt-tolerant and salt-sensitive rice seedlings after salt stress.
abstract: Salinization plays a primary role in soil degradation and reduced agricultural productivity. We observed that salt stress reversed photosynthesis and reactive oxygen scavenging responses in leaves or roots of two rice cultivars, a salt-tolerant cultivar Pokkali and a salt-sensitive cultivar IR-29. Salt treatment (100 mM NaCl) on IR-29 decreased the maximum photochemical efficiency (Fv/Fm) and the photochemical quenching coefficient (qP), thereby inhibiting photosynthetic activity. By contrast, the salt treatment on Pokkali had the converse effect on Fv/Fm and qP, while increasing the nonphotochemical quenching coefficient (NPQ), thereby favoring photosynthetic activity. Notably, chloroplast or root cells in Pokkali maintained their ultrastructures largely intact under the salt stress, but, IR-29 showed severe disintegration of existing grana stacks, increase of plastoglobuli, and swelling of thylakoidal membranes in addition to collapsed vascular region in adventitious roots. Pokkali is known to have higher hydrogen peroxide (H2O2)-scavenging enzyme activities in non-treated seedlings, including ascorbate peroxidase, catalase, and peroxidase activities. However, these enzymatic activities were induced to a greater extent in IR-29 by the salt stress. While the level of endogenous H2O2 was lower in Pokkali than in IR-29, it was reversed upon the salt treatment. Nevertheless, the decreased amount of H2O2 in IR-29 upon the salt stress didn't result in a high scavenging activity of total cell extracts for H2O2, as well as O2(·-) and (·)OH species. The present study suggests that the tolerance to the moderate salinity in Pokkali derives largely from the constitutively maintained antioxidant enzymatic activities as well as the induced antioxidant enzyme system.
authors.affiliation: Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, 29 Gunmgu-gil, Jeongeup-si, Jeollabuk-do 580-185, Republic of Korea.
authors.forename: Min Hee
authors.initials: MH
authors.lastname: Lee
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Cho
authors.forename: Seung Gon
authors.initials: SG
authors.lastname: Wi
authors.forename: Hyoungwoo
authors.initials: H
authors.lastname: Bae
authors.forename: Ji Eun
authors.initials: JE
authors.lastname: Kim
authors.forename: Jae-Young
authors.initials: JY
authors.lastname: Cho
authors.forename: Sungbeom
authors.initials: S
authors.lastname: Lee
authors.forename: Jin-Hong
authors.initials: JH
authors.lastname: Kim
authors.forename: Byung Yeoup
authors.initials: BY
authors.lastname: Chung
mesh_terms: D000975:Antioxidants; D002374:Catalase / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000378:metabolism*; D012275:Oryza / Q000033:anatomy & histology / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D010788:Photosynthesis / Q000187:drug effects*; D059828:Plant Cells / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects; D018517:Plant Roots / Q000187:drug effects; D055049:Salt Tolerance; D036226:Seedlings / Q000187:drug effects; D012965:Sodium Chloride / Q000009:adverse effects / Q000378:metabolism*; D013045:Species Specificity; D013312:Stress, Physiological
chemical_list: D000975:Antioxidants; D012965:Sodium Chloride; D006861:Hydrogen Peroxide; D010544:Peroxidases; D002374:Catalase
keywords: (1)O(2); AA; APX; Antioxidative enzyme; CAT; CO(2); Chl; H(2)O(2); HO(2); MS; Murashige and Skoog; NPQ; O(2)(−); OH; Oryza sativa L.; POD; PS II; Photosynthesis; ROS; Reactive oxygen species; SOD; Salt stress; TEM; achlorophyll a; ascorbate peroxidase; ascorbic acid; bchlorophyll b; carbon dioxide; catalase; hydrogen peroxide; hydroxyl radical; nonphotochemical quenching; perhydroxyl radical; peroxidase; photochemical quenching coefficient; photosystem II; qP; reactive oxygen species; singlet oxygen; superoxide anion; superoxide dismutase; tCar; tChl; total carotenoids; total chlorophylls; transmission electron microscopy